Add slang shader for shadow mapping and shadow mapping cascades sample

shaders/slang/shadowmappingcascade/depthpass.slang

@@ -0,0 +1,46 @@
+/* Copyright (c) 2025, Sascha Willems
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ */
+
+struct VSInput
+{
+    float3 Pos;
+    float2 UV;
+};
+
+struct VSOutput
+{
+    float4 Pos : SV_POSITION;
+    float2 UV;
+};
+
+// todo: pass via specialization constant
+#define SHADOW_MAP_CASCADE_COUNT 4
+
+struct UBO {
+    float4x4 cascadeViewProjMat[SHADOW_MAP_CASCADE_COUNT];
+};
+[[vk::binding(3, 0)]] ConstantBuffer<UBO> ubo;
+
+[[vk::binding(0, 1)]] Sampler2D colorMapSampler : register(s0, space1);
+
+[shader("vertex")]
+VSOutput vertexMain(VSInput input, uniform float4 meshPosition, uniform uint cascadeIndex)
+{
+    VSOutput output;
+    output.UV = input.UV;
+    float3 pos = input.Pos + meshPosition.xyz;
+    output.Pos = mul(ubo.cascadeViewProjMat[cascadeIndex], float4(pos, 1.0));
+    return output;
+}
+
+[shader("fragment")]
+void fragmentMain(VSOutput input)
+{
+    float alpha = colorMapSampler.Sample(input.UV).a;
+	if (alpha < 0.5) {
+		clip(-1);
+	}
+}